1. Field of the Invention
The present invention relates to a connector to be mounted on an external board, a connector mounting structure for mounting the connector on the external board, and a method of manufacturing the connector to be mounted on the external board.
2. Description of the Related Art
Data transmission systems include an ordinary transmission system and a differential transmission system. The ordinary transmission system employs an electric wire for each data item. The differential transmission system, using a pair of electric wires for each data item, simultaneously transmits a “+” signal to be transmitted and a “−” signal equal in magnitude and opposite in direction to the “+” signal. The differential transmission system, which has the advantage of being less susceptible to noise compared with the ordinary transmission system, is widely used in fields where signals are transmitted at high speed.
FIG. 1 is a schematic perspective view of a conventional differential transmission connector unit 1.
The differential transmission connector unit 1 includes a plug connector 2 and a jack connector 3. The plug connector 2 is mounted on a backplane (external board) 4. The jack connector 3 is mounted at an end of a daughterboard (external board) 5. The jack connector 3 and the plug connector 2 are connected so that the daughterboard 5 and the backplane 4 are electrically connected by the connector unit 1. (See, for example, United States Patent Application Publication No. 2008/0108233 A1.)
FIG. 2 is an exploded perspective view of the conventional jack connector 3.
As illustrated in FIG. 2, the jack connector 3 includes a first insulative housing 6, a second insulative housing 7, and multiple modules 10. The first insulative housing 6 is configured to be fit in a housing 8 (FIG. 1) of the plug connector 2. The second insulative housing 7 is configured to support the modules 10 parallel to each other.
FIG. 3 is a schematic perspective view of the conventional module 10. FIG. 4 is an exploded perspective view of the conventional module 10.
Referring to FIG. 3 and FIG. 4, the module 10 includes a wiring board 11 with multiple pad electrodes 16; multiple leads 12 for electrically connecting the wiring board 11 and the external board 5 (FIG. 1); multiple solder layers (conductive layers) 17; and an insulative spacer 13. The leads 12 are connected to the corresponding pad electrodes 16 through the corresponding solder layers 17.
FIG. 5 is a cross-sectional view of part of the conventional module 10.
The spacer 13 is fixed on the wiring board 11. The spacer 13 has multiple guide grooves 132 on its surface facing the wiring board 11. The guide grooves 132 extend in a direction in which the leads 12 extend. The leads 12 are allowed to move inside the corresponding guide grooves 132 when the solder layers 17 melt.
FIG. 6A is a front-side cross-sectional view of the conventional jack connector 3 placed on the daughterboard 5. FIG. 6B is a schematic cross-sectional view of the jack connector 3 of FIG. 6A taken along one-dot chain line A-A.
A solder paste 19 for bonding the leads 12 is applied on the surface of the daughterboard 5. In the case illustrated in FIGS. 6A and 6B, there is a gap between some of the leads 12 and the solder paste 19 because of the warpage of the daughterboard 5.
FIG. 7A is a front-side cross-sectional view of the conventional jack connector 3 placed on the daughterboard 5 after heating (reflow soldering). FIG. 7B is a schematic cross-sectional view of the jack connector 3 of FIG. 7A taken along one-dot chain line A-A.
When the solder paste 19 is melted by heating, each solder layer 17 melts, so that the leads 12 are movable inside the corresponding guide grooves 132. In this state, the leads 12 are pushed into the corresponding guide grooves 132 because of gravity so as to absorb the warpage of the daughterboard 5. As a result, the leads 12 are connected to the daughterboard 5 after heating.